This site sounds rather interesting but I can hardly find any information on it - perhaps someone local can provide enlightenment. (The combination of barrow and spring attracted me - but of course may be totally coincidental).
Blood Hill is a round barrow only about a mile from Grimes Graves, on a path through Thetford Forest. It has a tantalising name - behind which there must surely be a good story? Some kind of prehistoric boundary bank is also associated with the mound.
A stone's throw downhill is the holy well of St Helen (once contracted to 'Tenant's Well' according to the smr) and the remains of her church (St Helen's Oratory). The parish boundary (and the railway) run close by. A long distance footpath passes the site, so it should be quite accessible.
The water from the spring runs into the Little Ouse - if you look on the map there are a couple of other barrows nearby along this stretch of the river valley too.